Portable power tools such as a type disclosed in U.S. Pat. No. 3,908,139 to Duncan, Jr., or U.S. Pat. No. 4,223,744 to Lovingood generally comprise a motor housing unit and a tool head housing clamped with screws thereto to project forwardly from the motor housing. A bearing plate is provided for journaled reception of a motor shaft and spindle and intermediate shafts supporting the gear train within the tool head. In the prior art designs noted above, this bearing plate forms an external seam with both the tool head and motor housing which often, and disadvantageously, causes a contour mismatch between the motor housing, bearing plate and tool head. Additionally, in the aforesaid known designs, considerable and precise machining of the bearing plate with two rabbet diameters respectively on opposite sides of the plate is required for mounting said plate to the housings.
Another difficulty associated with the foregoing designs is the requirement of a separate nut plate, often referred to in the art as a strip nut, which must be mounted within the motor unit housing as a separate part from the bearing plate to secure the tool head to the motor housing. The provision of a separate screw or nut plate increases the weight of the portable tool and also results in further machining requirements in the fabrication of this part, resulting in an increased manufacturing cost.
It is accordingly one object of the present invention to provide a bearing plate within a portable power tool that is multi-functional, serving as a bearing mounting plate and a nut plate for clamping the tool head to the motor housing unit.
Another object is to provide a bearing plate that also serves as a three-position auxiliary handle mount.
It is another object of the present invention to provide a bearing plate that is mounted internally within the motor unit housing, resulting in the elimination of an external seam between the bearing plate and the motor housing or tool head which may otherwise result in a possible contour mismatch.
Still another object is to provide a bearing plate that results in an overall reduction of length of the power tool by virtue of the internal mounting arrangement of the bearing plate within the power unit housing.
Still another object is to provide a bearing plate having simplified machining requirements.
Yet a further object is to provide a bearing plate having plural auxiliary handle mounts in the form of lugs positioned adjacent air vents in the motor housing for better cooling of bearings due to heat sink action of aluminum in the air stream.
Still another object is to provide a bearing plate eliminating an external seam, as occurs between the motor housing and tool head in prior art designs, and which further results in lower weight of the portable power tool by enabling the bearing plate to function as a nut plate, thereby eliminating a separate part.